Hydroreforming and reactivation of catalyst with an oxygen containing gas



United States Patent HYDROREFORMING AND REACTIVATION OF CATALYST WITH ANOXYGEN CONTAINING GAS Claims. (Cl. 208-436) This invention relates to acatalytic process for the treatment of hydrocarbons to convert them tomore valuable products. More particularly, the invention relates to aprocess for the catalytic reforming of hydrocarbons of the naphtha orgasoline boiling range to in crease the value of such hydrocarbons ascomponents of fuels for internal combustion engines.

The petroleum industry for years has been faced with a demand forgasolines of progressively higher anti-knockquality. For some timerefiners have met the demand with catalytic cracking supplemented byprocesses such as thermal reforming, polymerization, alkylation, etc.However, catalytic cracking is limited in its ability to upgrade thewhole refinery gasoline pool. The other processes have had variouseconomic drawbacks. The continued demand for gasolines of still higheroctane ratings for use in high compression automotive engines forced therefiners to seek a new way of upgrading low octane stocks. In recentyears a type of process has been developed that, when coordinated withthe other refinery operations, offers economic advantages for mostrefiners over any other process for improving the anti-knock propertiesof stocks such as straight run and natural gasolines. The process werefer to is catalytic reforming in the presence of hydrogen, orhydroreforming as it is commonly called.

Its economic advantages have caused hydroreforming to be widely adoptedand it has become one of the most important of refining processes.Several variations of the hydroreforming process are now in use. Theyvary somewhat in operating conditions and in the particular type ofcatalyst used. They have in common the fact that a gasoline or naphthafraction is contacted with a catalyst in the presence of a large amountof hydrogen at a temperature above about 750 F. and usually at anelevated pressure. The treatment results in chemical conversion ofcomponents of the charge to materials of better anti-knock propertiesbut without a great change in average molecular weight of the charge. Anumber of chemical reactions can take place in the hydroreformingprocess. These include (1) conversion of cyclopentane with methyl sidechains to cyclohexane; (2) conversion of cyclohexane to aromatics with alarge yield of hydrogen; (3) cracking of higher molecular weightparaflins; (4) hydrogenation of olefins formed as intermediate crackingproducts; (5) conversion of sulfur compounds to hydrogen sulfide; and(6) isomerization of normal parifiins to branched-chain parafiins. Theproduct in general contains a higher proportion of aromatics andisoparaflins than the charge and usually has a slightly lower averagemolecular weight than the charge.

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The competition to produce high octane gasolines has caused the processof hydroreforming to be studied in all details to find ways ofincreasing the yield and quality of the gasoline product. Manyimprovements have been made in the process since its first development.The present invention is especially significant because it providesimprovement in a most important refining process that has already beenbrought in the prior art to a high state of efliciency.

Broadly, our invention pertains to an improvement in hydroreformingprocesses which use catalysts containing molybdenum or its oxides. Theprocess of the invention is based on the discovery that a particularcombination of catalyst reduction technique and on-stream conditionsimproves the results of the process, as compared with prior arthydroreforming, by producing 'a gasoline product of higher yield and/ orof higher octane rating. The exact reasons for the improvement are notknown with certainty but it is believed that the process of theinvention renders the catalyst more selective for the reactions ofhydroreforming that are most important for raising octane rating, forexample, the aromatization of naphthenes and the isomerization ofstraight-chain parafiins, without excessively increasing the activityfor reactions such as cracking that reduce liquid yield.

Wehave discovered, in accordance with the invention, that by reducingthe reforming catalyst with hydrogen that contains a minor amount of anoxygenic gas such as steam, oxygen or carbon dioxide and then using thiscatalyst in an on-stream hydroreforming operation with hydrogen that issubstantially free of such oxygenic gases, an unexpected improvement inyield-octane relationship of the product occurs. The enhancement of thecatalyst activity by our reduction procedure remains in effect for aconsiderable time and produces the advantages of the invention for theusual throughput period with the molybdenum catalyst.

The hydroreforming process of our invention is most suitable forupgrading low octane stocks such as natural or casing-head gasolines andstraight-run naphthas or gasolines. Natural gasoline is the volatileproduct obtained by the recovery of normally liquid hydrocarbons fromnatural gas by a process such as absorption. Straight-run gasolines areproduced by fractionation of crude petroleum oil. The charge stocks forour process can also be blends of these types of stocks or blends withnaphthas obtained from other processes such as thermal or catalyticcracking. Our process shows an improvement 1n octane-yield relationshipover conventional hydroreforming whether the charge stock ispredominantly paraflinic or naphthenic.

The catalyst of our process is a molybdenum oxide type of reformingcatalyst. The molybdenum oxide can be used alone, but preferably isdeposited on a support or carrier. Suitable carriers include activatedalumina, alumina gels, peptized alumina gels, silica gels, silicaaluminagels, aged or deactivated silica-alumina cracking catalysts,silica-magnesia gels, magnesia, titania, bauxite and the like. Apreferred support consists of alumina stabilized with about 5 percent byweight silica. Although molybdenum is an essential element, otherreforming catalyst metals or oxides, for example, cobalt and nickel, canbe present in the catalyst.

Our process can be carried out in any of the systems for catalyticcontact that are suitable for reforming. For

example, the catalyst can be in pelleted or granular form in astationary fixed bed. It can also be in a finely divided or powderedform in a fluidized bed. The fluidized bed can be either a fixed fluidbed or a moving fluid bed. In a fixed bed system, either of the fluid orstationary type, the catalyst is kept in the same vessel for all cyclesof the process, that is, for the on-stream period and for theregeneration and reduction. In the moving fluid bed the catalyst iscontinuously transported from the hydroreforming vessel to other zonesfor regeneration and/r hydrogen reduction.

In discussing the range of operating conditions for our process we willdeal with the reduction stage first. In general, the reduction can becarried out at temperatures from about 850 F. to about 1200 F. Atemperature between about 1000 F. and 1100" F. produces the bestresults. However, the lower temperatures have the advantage of beingcloser to temperatures preferred for the on-stream hydroreforrningstage. If the reduction and on-stream temperatures are the same, loss oftime for cooling the catalyst before placing it on-stream can beavoided.

The other operating conditions of the reduction stage can varyconsiderably. The pressure can range from atmospheric to about 2000pounds per square inch. (This is gauge pressure, as are the otherpressures mentioned in the specification and claims.) It is advantageousto reduce the catalyst at either the pressure used during regenerationor the pressure used during the on-stream stage. The linear velocity ofthe reducing gas can vary consid- 'erably. We have found that rates offrom about 0.01 to 1.0 foot per second give good results in a fluid bedsystem. In general, a reduction period of from about 0.1 to 5.0 hours issutficient. In a moving bed fluid catalyst system the reduction can takeplace while the oxidized catalyst is being transported from theregenerator to the reactor by a stream of hydrogen. As we haveindicated, the most important feature of the reduction stage of ourprocess is the use of hydrogen that contains a minor amount of anoxygenic gas selected from the group consisting of steam, oxygen andcarbon dioxide.

When steam is used as the oxygenic substance for mixing with thereducing hydrogen, a concentration of from 0.5 to 10 or 15 mol percentor even higher will produce the advantages of the invention. Our bestresults are obtained with steam concentrations of from 0.5 to 5 molpercent, based on the hydrogen. The other oxygenic substances should beused in concentrations equivalent to these steam concentrations. For anequivalent effect, oxygen and carbon dioxide can be used in one-half themol percent concentration used for steam. If oxygen is used, care shouldbe taken that its concentration in the hydrogen does not exceed theexplosive limit.

After the reduction stage of our process, the catalyst is used forhydroreforming. The processing conditions can vary considerably,depending on the stock being treated and the balance of octane ratingand yield of product desired. The most significant feature of theonstream stage of our process is that the charge, that is, the mixtureof hydrocarbons and hydrogen with which the catalyst is contacted, issubstantially free of oxygenic substances.

The processing conditions for the on-stream hydroreforming stage of ourprocess can be as follows: The temperature is above about 750 F. andpreferably from about 850 F. to 1100" F. The pressure can range fromatmospheric pressure to high pressures of the order of 2000 pounds persquare inch. Pressures of from 50 to 500 pounds per square inch arepreferred. The space velocity can be from about 0.25 to 10.0 liquidvolumes of hydrocarbon per hour per volume of catalyst (based on denselypacked catalyst volume). Generally, a space veloclty of about one-halfto three vol./vol./hour is preferred. The hydrogen concentration, 0 hy gto naphtha ratio, should be at least about 500 standard cubic feet ofhydrogen per barrel of liquid hydrocarbon charge (42 U.S. gallons) andnot more than about 20,000 s.c.f. per barrel. At the start of theprocess it may be necessary to supply the hydrogen from an outsidesource. However, the dehydrogenation that occurs in hydroreforming willusually produce enough hydrogen so that the hydrogen requirements can bemet by recycle from the product.

' Having described the general and preferred ranges of conditions forour process, we will now describe some actual hydroreforming runs thatwe have carried out by the method of our invention and by a conventionalhydroreforming technique, using the same naphtha charge stock for allruns. The results of these runs offer a comparison of the differentmethods and show the superiority of our process over the conventionalprocess.

The charge stock in this series of runs was a straightrun naphtha from aKuwait crude oil. The naphtha was hightly paraffinic and had a very lowoctane rating. The inspection data for this naphtha are as follows:

KUWAIT NAPHTHA INSPECTION DATA Gravity, API 52.6 Sulfur, wt. percent0.109 Reid vapor pressure, lbs/in. 1.5

Hydrocarbon type analysis:

Paraffins, vol. percent 64.6 Naphthenes, vol. percent 22.0 Olefins, vol.percent 0.8 Aromatics, vol. percent 12.6 Distillation:

Initial boiling point, F. 237 10% 292 50% 327 v 374 End point 406 OctaneNo. (Micro) Research Method:

Clear 22.2 +3 cc. TEL/ gal 47.2

Each of the runs was carried out in a fixed fluid-bed reaction systemusing a powdered molybdena-on-alumina reforming catalyst. The catalystconsisted of 10.8 percent by weight molybdenum trioxide impregnated onalumina coprecipitated with about 5 percent silica. Before starting theseries of runs the catalyst was calcined overnight in air at 1000 F. andfor three hours at 1100 F. The catalyst was then treated in accordancewith the invention as described in the specific example below.

Example The calcined catalyst was reduced with purified hydrogencontaining 4.7 mol percent steam at a temperature of 900 F., a pressureof 250 pounds per square inch gauge and a linear gas velocity of 0.1foot per second for one hour. Then a mixture of the Kuwait naphthadescribed above and hydrogen in proportions of 5000 standard cubic feetof hydrogen per barrel of naphtha was charged to the fixed bed fluidizedcatalyst. The hydrogen used during this period was substantially free ofsteam or other oxygenic substances. It contained less than about 0.01mol percent steam. The reaction conditions included an averagetemperature of 903 F., a pressure of 250 pounds per square inch, and aspace velocity of 1.0 liquid volume of naphtha per volume of catalyst.per hour. The mixture of hydrocarbons and hydrogen was charged to thecatalyst bed for a period of three hours. During the first hour of thethree hour period, all operating variables were lined out. The secondtwo hours was the on-stream period during which products were collected.

At the end of this first run, the catalyst was flushed with hydrogen,depressured, flushed with nitrogen, and then regenerated to remove cokedeposits. The regeneration was carried out by flowing air through thecatalyst for one hour at temperatures in the range of 900 to 1100 F. toburn oiI the deposited coke.

6' Table II gives a comparison of a run by our method and a runfollowing conventional procedure. Results are reported on the basis ofthe C4+ or depropanized gasoof 2.0 points of octane rating is, ofcourse, very significant at this high octane level. Comparing runs 2 and3, it is seen that the difierence in octane ratings of the product isless than between runs 1 and 4 but that the yield difierence is greater.Very clearly our process has improved the yield-octane relationship.

The catalyst described in the example was then used line product. Run 5,in which the catalyst was reduced in a number of other runs. Certain ofthe runs followed 5 with hydrogen containing steam in the method of theinthe method of the invention, using in the reduction stage vention,produced a C gasoline of greater yield and hydrogen that contained asubstantial proportion of higher clear octane rating than run 6, carriedout by consteam. The other runs followed a conventional method,ventional procedure with catalyst reduction with hydrousing for both thereduction and on-stream stages hygen containing no steam. drogen thatcontained less than 0.01 percent steam. Some of the runs, either by themethod of the invention TABLE III or by the conventional method, usedthe reduction temperature of 900 F., described in the example above.Hydrogen Hydrogen Other runs by both methods used a reduction temperwithithoi n ature of 1050 F. The specific operating conditions for 5 5 31 38,; 5 3353,, the reduction stage and the hydroreforming stage for eachRun 7 8 of the runs are given in Tables I through VIII below.

The tables also give results for each run in terms of 7 Reductionconditions: yield and octane ratings of gasoline products. Temperature,0 F 900 V 9 Steam content of hydrogen, moi percent... 5. 4 0. 01

Processing cond1tions: TABLE I Temperature, F 901 901 Pressure p.s.1.g.250 250 1Sflpace vfil;] 1city,tyol./v %l7{)h'r1 r $0 1.0 Hydrogen withHydrogen withr 00 100 Steam out Steam 10 szl giitifniie y 'veiume 77 174 5 ductlon reduction Octane number, micro research iieiij ji 93.5 92:7

Run 1 2. 3 4

Table III gives a comparison of a run by the method of Reductionconditions:

Tempemtm, F 900 900 900 900 he nvention and a run by conventionalprocedure on the Steam content of hydrogen, mol basis of the yield andoctane rating of the unleaded gasog gg line product adjusted to 2. Reidvapor pressure of 10 gem ereane, F pounds per square inch by addingbutanes. The product ressure P.S. .g space ve'locityvouvouhn L0 L0 L0for our process, run 7, is superior both in yield and no 0 nen ht no,s.c.f./bbl. 4, 000 5,000 5, 100 tane rating. The yield advantage is 2.6percentage pomts gf h g volume 6&2 615 6&6 and the octane advantage 0.8point at a high octane level.

Octane number, micro research (clear) 93.6 92.9 92.1 91.6 TABLE HydrogenHydrogen In Table I the yields and octane numbers are given 40 stwithfor vitl r rt for C gasoline product. These data were obtained gig i f gigf, by standard calculations which adjusted the data obtained R 5 a un 910 by analysis of the raw gasoline product to data for a debutamzedgasoline, free of butanes and lighter hydro- Reduction conditions:

- carbons. Table I shows that the use of steam during the Temp9ram1re, F900 900 catalyst reduction at 900 F. in runs 1 and 2 substantially 0fFYdmgen, Percent-u 01 Processing conditions. improved the yield-octanerelationship of the C prod- '1I emperature, F 901 00s ressure, p.s.i.g250 250 uct. Comparing runs 1 and 4 1n which yields were about spaceVelocity, VOL [VOL 1hr L 0 1 0 equal, the octane number of the clear Cproduct was 10 r r g ne ighe r n e, s.c.f./bbl- 5,200 5,000

I pro uc a a: 93.6 for ur pr ss 1) g steam 1n t hydrogen Yield, byvolume m 74, 2 reduction stage and 91.6 for the conventional processOctane number, micro research (+3 cc. 1 (run 4)'using dry hydrogen forreduction. This increase TEL) 4 100-0 1 Performance number.

Table IV gives a comparison of our process and the conventional processon the basis of the yield and octane rating of the gasoline productadjusted to a 10 pound Reid vapor pressure and containing 3 cc. oftetraethyl lead per gallon. The octane rating for the product of ourprocess, run 9, is substantially better and the yield is about 3percentage points higher than that of the conventional process, run 10.

Tables I through IV show that the advantages for our process are notlimited to any particular way of measuring results. The results on fourdificrent standard methods of calculating the product yield and octanerating show our process superior in every case. Tables V through VIIIbelow record the results of runs in which the reduction temperature was1050 F. In these runs the catalyst, after reduction at 1050" F., wascooled to the run temperature of about 900 F. in the presence of thehydrogen containing steam or the dry hydrogen used in the reduction. Thecooling required about 30 minutes. Specific conditions and results foreach run are given in the tables.

TABLE V Hydrogen with Hydrogen withsteam for reout steam for ductionreduction Run 11 12 13 14 Reduction conditions:

Temperature, F 1, 050 1, 050 1, 050 1, 050

Steam content of hydrogen, mol

Table V gives a comparison of our process and the conventional processwhen a reduction temperature of 1050 F. is used. The comparison is basedon the or debutanized clear gasoline product. The octane rating for theproduct of our process in run 12 was 3.2 points higher than that of theconventional process in run 14. The yield for our process was alsosomewhat greater. Table V shows that the advantages of our process areobtained with difierent steam concentrations in the hydrogen reductionstage. Run 11 used a steam concentration of 4.7 mol percent and run 12 asteam concentration of 2.0 mol percent. The octane-yield relationshipsof the products for both of these runs were superior to those for theconventional process runs 13 and 14.

Table VI compares our process with the conventional process, using areduction temperature of 1050 F., on the basis of the C clear gasolineproduct. The table shows that our process produces advantages when asteam concentration as low as 0.5 mol percent is used in the reductionstage. Run 15, in which the catalyst was reduced with hydrogencontaining 0.5 mol percent steam, yielded a C.,-{- product that was 3.2percentage points better in yield and 2.4 points better in octane rating(clear) than the product of the conventional process, run 16.

TABLE VII Hydrogen Hydrogen with without steam for steam for reductionreduction Run 17 18 Reduction conditions:

Temperature, F 1, 050 1, 050 Steam content of hydrogen, mol percen 2.00. 01 Processing conditions:

Temperature, F 902 901 Pressure, p.s.i.g 250 2:0 Space velocity,vol./vol./hr -1. 0 1.0 Hqznaphtha ratio, s.c.i./hbl 5, 000 5, 200 RV?product data:

Yield, percent by volume.. 79.6 79.0 Octane number, micro research(clear) 92. 6 89. 8

Table VII compares the product of our process when a reductiontemperature of 1050 F. is used with that of the conventional process onthe basis of the unleaded gasoline product adjusted to a 10 pound Reidvapor pressure. The product of our process, run 17, was somewhatsuperior in yield and had a clear octane rating of 2.8 points above thatof the product of conventional process, run 18.

TABLE VIII Hydrogen Hydrogen with without steam for steam for reductionreduction Rim 1!? 20 Reduction conditions:

Temperature, F 1, 050 1, 050 Steam content of hydrogen, mol percent.-.4. 7 0. 01 Processing conditions:

Temperature, F 901 001 Pressure, p.s.i.g 250 250 Space velocity,vol./vol./hr 1.0 1.0 Hfinephtha ratio, s.c.f./bbl 5, 000 5, 200 10 RV?product data:

Yield, percent by volume 82.7 79. 0 Octane number, micro research: +3cc.

TEL 100.0 99. 0

Table VIII compares our process with the conventional process, using areduction temperature of 1050 F., on the basis of the gasoline productadjusted to a 10 pound Reid vapor pressure and containing 3 cc. oftetraethyl lead per gallon. The product of our process, run 19, wassuperior in yield by 3.7 percentage points and in octane rating by 1.0point as compared with the product of the conventional process, run 20.

The tables above show that our process gives a product with ayield-octane relationship superior to that of the product of theconventional process on any standard basis of calculation. The tablesalso show that the superiority of our process exists over a considerablerange for the concentration of steam in the hydrogen used in thereduction stage of our process and over a considerable range for thetemperature of reduction.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A catalytic reforming process which comprises reducing a reformingcatalyst comprising molybdenum oxide with hydrogen containing anoxygenic gas selected from the group consisting of steam, oxygen andcarbon dioxide in a concentration equal in oxygen content to 0.5 to 15mol percent of steam and contacting the reduced catalyst underhydroreforming conditions with a charge comprising naphtha and hydrogen,said charge being substantially free of oxygenic gases.

2. A catalytic reforming process which comprises contacting a reformingcatalyst comprising molybdenum oxide with hydrogen containing anoxygenic gas selected from the group consisting of steam, oxygen andcarbon dioxide in an amount equal in oxygen content to 0.5 to 15 molpercent of steam at a temperature from 850 to 1200 F., and contactingthe resulting catalyst under hydroreforming conditions with a chargecomprising naphtha and hydrogen, said charge being substantially free ofoxygenic gases.

3. A hydroreforming process which comprises reduring a catalystcomprising molybdenum oxide with hydrogen containing a gas selected fromthe group consisting of steam, oxygen and carbon dioxide in aconcentration equal in oxygen content to 0.5 to 5 mol percent of steam,at a temperature from 1000" to 1100 F. and a pressure above 50 poundsper square inch, and contacting the resulting reduced catalyst with acharge comprising naphtha and hydrogen in proportions of at least 500cubic feet of hydrogen per barrel of naphtha, said charge beingsubstantially free of oxygenic gases and said contacting being underhydroreforming conditions including the pressure used in reducing thecatalyst and a temperature above 750 F.

4. A hydroreforming process which comprises reducing a regeneratedreforming catalyst comprising molybdenum oxide supported on an aluminacarrier with hydrogen containing from 0.5 to 5 mol percent steam at atemperature from 1000 to 1100 F. and a pressure above 50 pounds persquare inch, contacting the resulting reduced catalyst in a reactionzone with a charge comprising a straight-run naphtha and hydrogen inproportions of from 1,000 to 20,000 cubic feet of hydrogen per barrel ofsaid naphtha, said charge being substantially free of oxygenic gases andsaid contacting being under hydroreforming conditions including thepressure used in reducing the catalyst and a temperature above 750 F.

5. A catalytic reforming process which comprises in a reduction stagereducing a regenerated reforming catalyst comprising molybdenum oxidewith hydrogen containing an oxygenic gas selected from the groupconsisting of steam, oxygen and carbon dioxide in a concentration equalin oxygen content to 0.5 to 15 mole percent of steam and thereafter in areforming stage contacting under hydroreforming conditions a chargecomprising naphtha and hydrogen, said charge being substantially free ofoxygenic gases, with a body of catalyst consisting essentially of thereduced, regenerated catalyst reduced according to the procedure of saidreduction stage.

References Cited in the file of this patent UNITED STATES PATENTS2,270,715 Layng et a1. Ian. 20, 1942 2,274,988 Matuszak Mar. 3, 19422,700,639 Weikart Jan. 25, 1955 2,710,827 Gornowski June 14, 19552,772,217 Nicholson Nov. 27, 1956

5. A CATALYTIC REFORMING PROCESS WHICH COMPRISES IN A REDUCTION STAGEREDUCING A REGENERATED REFORMING CATALYST COMPRISING MOLYBDENUM OXIDEWITH HYDROGEN CONTAINING AN OXYGENIC GAS SELECTED FROM THE GROUPCONSISTING OF STEAM, OXYGEN AND CARBON DIOXIDE IN A CONCENTRATION EQUALIN OXYGEN CONTENT TO 0.5 TO 15 MOLE PERCENT OF STEAM AND THEREAFTER IN AREFORMING STAGE CONTACTING UNDER HYDROREFORMING CONDITIONS A CHARGECOMPRISING NAPHTHA AND HYDROGEN, SAID CHARGE BEING SUBSTANTIALLY FREE OFOXYGENIC GASES, WITH A BODY OF CATALYST CONSISTING ESSENTIALLY OF THEREDUCED, REGENERATED CATALYST REDUCED ACCORDING TO THE PROCEDURE OF SAIDREDUCTION STAGE.